Role of Scirpus mariqueter on Methane Emission from an Intertidal Saltmarsh of Yangtze Estuary

The role of wetland plant (Scirpus mariqueter) on methane (CH4) emissions from a subtropical tidal saltmarsh of Yangtze estuary was investigated over a year. Monthly CH4 flux and pore-water CH4 concentration were characterized using static closed chamber technique and pore-water extraction. Measured chamber CH4 fluxes indicated that saltmarsh of the Yangtze estuary acted as a net source of atmospheric CH4 with annual average flux of 24.0 mgCH4·m−2·day−1. The maximum chamber CH4 flux was in August (91.2 mgCH4·m−2·day−1), whereas the minimum was observed in March (2.30 mgCH4·m−2·day−1). Calculated diffusion CH4 fluxes were generally less than 6% of the chamber fluxes. Significant correlations were observed between the chamber CH4 flux and rhizospheric pore-water CH4 concentration (11–15 cm: p < 0.05, R = 0.732; 16–20 cm: p < 0.05, R = 0.777). In addition, chamber CH4 fluxes from July to September constituted more than 80% of the total annual emission and were closely correlated with aboveground biomass yield of S. mariqueter. The results indicated that S. mariqueter transportation was the dominant CH4 emission pathway and it provided an efficient route for the belowground CH4 to escape into the atmosphere while avoiding oxidation, leading to CH4 emissions.